SEO or Search Engine Optimisation is a set of internal operations done to your website. As the name suggests, SEO means optimising your website so search engines can better index your pages and the content within them. That is, your pages appear higher in results for relevant, targeted key phrases than competing websites. This is important because Search Engines are known to bring upto 80% of traffic to your website!!!
For example, you may have a website that sells digital cameras. Your webpages have lots of info on models, price, features etc. You may also have a special page within the website that gives tips to amateur photographers. Now you would want this page to come up in search results in Google, Yahoo etc. apart from your main pages because amateur photographers, after reading your tutorial, may make a purchase through your site.
RCorp SEO (Search Engine Optimisation)makes sure Search Engines take notice of every single word, every single image, every single video of every single page in your website.